Telephone-exchange system.



H. W. MACDOUGALL.

TELEPHONE EXCHANGE SYSTEM. APPLICATlON FILED IULY 2.1917.

- Affy.

stra ns HARRY W. MAcDOIJ'GALL, OF EAST ORA GE, NEW JERSEY, AssrenoR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION, OF

NEW YORK.

TELEPHONE-EXCHANGE SYSTEM;

Patented July 16', 1918.

Application filed July 2, 1917. Serial No. 178,163.

To all whom. it may concern:

Be it knownv that 1,,HARRY XV. MAC- DOUGALL, a citizen of the United States, residing at East Orange, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Telephone-EXcha-nge Systems, of which the following is a full, clear, concise, and exact description.

This invention, relates to telephone exchange systems, and more particularly to such systems in, which ringing current is automatically applied. to a wanted line upon the connection of a link circuit therewith.

An object of thisinvention. is the production of improved signaling means for such systems. I

Another object of this invention is the provision of a system of this. character in which it is impossible to ring a. subscriber in the ear.-

In accordance with this invention, a link circuit of the automatic ringing type is provided with apparatus for preventing the connection of the source of ringing current to a busy line or a line the receiver of which is removed from, the switchhook when the link circuit is connected with such a line.

Apparatus is also provided, by means of which, when the link circuit is connected to a line of the character mentioned, a signaling ClEWlCQ is caused to furnish a character istic signal indicating to the operator that the line to which the link circuit hasbeen connected is either busy or the receiver thereof is ofi its switchhook. Should it be desired to telephonically connect the calling line with the busy line, the actuation of a switch or key in the link circuit by the operator stops the operation of the signaling device, and completes the talking, circuit between the calling line and the busy line.

For a more complete understanding of this invention, reference should be had to the following description, considered in connection with the accompanying drawing containing one embodiment thereof.

In the drawing, there is shown a calling telephone line A, connected in any desired manner with a cord circuit C, which may be employed to connect calling line A with another telephone line B. It will be understood that a number of lines similar to lines A and B, terminate at the same central ofiice, and that a number of cord circuits are proyided thereat for interconnecting these lines, but, for the sake of convenience, only two lines and the one cord circuit are shown.

Assuming that the operator has been ad vised that the calling subscriber A desires to be connected with subscriber B, the operator may test the terminal of line B in order to determine whether this line is idle or busy. Assuming that line B is busy, due to the connection of another cord circuit, Similar to G, with one of its jacks, the cutoff relay 5 of line B will be operated to dis: connect the line relay 6 from the line. Under these conditions, the operator may in scrt plug 7 of cord circuit G into jack 8 without making a. test. If the plug of the cord circuit C be inserted into the jack 8 while another cord circuit is connected with another jack of the same line. current will flow from battery in the other cord circuit over the ring talking strand thereof and the ring contacts of the engaged plug and jack, the ring contacts of the jack 8, and the plug 7, lower normal contact of relay 9, the windings of polarized relay 10, upper normal contact of relay 9, tip. contacts of the plug 7 and the jack 8 and back to the other side of battery in the cord circuit through the tip contacts of the other engaged jack and plug and the tip talking strand of the other cord circuit connected to line B. Relay 10 is polarized so as not to attract its armature when its windings are traversed by current flowing in the direction just traced. The insertion of the plug 7 into the jack 8 causes the operation of relay 11 over a circuit from battery through the winding of relay 11, upon normal contact of relay 12, sleeve contacts of the plug 7 and jack 8, and the winding of cut-off relay 5' to ground. Relay 11, in operating, opens its normal and closes its alternate contact. The opening of the normal contact of relay 11 introduces a break in the tip talking strand of the cord circuit C. The

another jack of I 11 operates as .over a circuit from battery,

closure of the alternate contact causes the intermittent operation of the calling supervisory lamp 13 over a circuit from battery through the lamp 13, alternate contact of relay 11, resistance 14:, and interrupter 15 to ground. The intermittent operation of the calling supervisory lamp indicates to the operator that the cord circuit has been connected with a busy line. The operator may thereupon advise the calling subscriber that line B is busy, jack 8 and disconnect the cord circuit C from the calling line A. V 1

In case, however, that lines of subscribers A and B had been previously connected together and had been accidentally disconnected before the conclusion of the conversation, the operator, upon connecting with line A, is advised that the" connection between subscribers A and B has been accidentally severed. The operator will, therefore, immediately insert plug 7 into jacks. Under these conditions, it may be that subscriber B has his receiver off the switchhook endeavoring to get the operator in order that connections may be reestablished with line A, so that, upon the insertion of the plug 7 into jack 8, the direction of the flow of current through the windings of polarized relay 10 is in the'direction to operate this relay. However, since the receiver of line B is off the switchhook, the circuit, including the line wires and the low resistance bridge at the 'subscribers station, forms a low resistance shunt in parallel with the winding of the polarized relay 10 and prevents the operation of this relay. Relay before, causing the intermittent operation of the supervisory lamp 13. The winding of relay 11 is of high resistance, so that when relay 11 is included in circuit with the cut-off relay 5, relay 11 operates but the cut-off relay 5 In order that the talking circuit between lines A and B may, under these conditions, be completed, the operator momentarily actuates a non-locking key 20. Upon the actuation of this key, relay 12 is operated through the lamp 13, winding of relay 12, upper alternate contact of key 20, and resistance 21 to ground. Relay 12, in operating, completes a locking circuit for itself from battery through lamp 13, winding of relay 12, upper alternate contact thereof, sleeve contacts of the plug 7 and jack 8 and the windin of cut-off relay 5 to ground. The cut 0 relay 5 now operates, disconnecting the line relay 6 from the line. Relay 12, in operating, causes the release of relay 11, whereupon the intermittent operating circuit for lamp 13 is opened. The lamp-13 is now continuously lighted over the circuit including relay 12 and the cut off relay 5.. The

and withdraw the plug 7 from does not operate.

actuation of key 20 also causes the operation of relay 25 over a circuit from battery through resistance 26, lower alternate contact of key 20, normal contact of relay 25 and winding thereof, and the lower alternate contact of relay 12 to ground. Relay 25, in operating, closes its alternate and opens its normal contact, and establishes, through its alternate contact, a locking circuit for itself. The closure of the alternate contact of relay 25 also establishes a direct short circuit for ringing relay 27 preventing its operation. Relay 12, in operating, also causes'the operation of relay 9, which opens its normal contacts, removing the polarized relay 10 from across the tip and ring contacts of the cord circuit, and closes its alternate contacts, completing the talking circuit between lines A and B. Immediately upon the operation of relay 9, the receiver at station B being 05 the switchhook, supervisory relay 28 operates to close a shunt circuit including a resistance 29 for the calling supervisory lamp 13', thereby extinguishing thislamp. Upon the conclusion of the conversation, the receiversoare restored to their switchhooks, thereby causing lighting of the supervisory lamps to furnish disconnect signals to the operator, who may then disconnect the cord'circuit from the lines, whereupon all apparatus is restored to normal condition.

If, when the plug 7 is inserted into the jack 8, the receiver at stationB is on the switchhook, there will not then exist the hereinbefore mentioned low resistance shunt circuit about the' polarized relay 10, but relay 10 does not operate until after the operation of relay 11, for while relay 11 remains in its normal position, there'exists a low resistance circuit in parallel with'the windings of relay 10. This circuit may be traced from the point 3 1 on the tip talking strand through the normal contact of relay 11, upper normal contact of relay 27, and repeating coil winding 33 to ground. Upon the operation of relay 11, which opens the low resistance parallel circuit,'the polarized relay 10 operates over a circuit from battery through right-hand winding of line relay 6, right-hand normal contact of cut-off relay 5, tip contacts of the jack 8 and the plug 7 upper normal contact of relay 9, windings of relay l0,'lower normal contact of relay 9, ring contacts of the plug 7 and the jack 8, left-hand normal contact of cut-off relay 5, and the left-hand winding of line relay 6 to ground. Polarized relay 10, in operating, closes its contact, thereby causing the operation of relay 12 over a circuit frombattery through the lamp 13, winding of relay 12,

contact of polarized relay 10, sleeve contactsof the plug 7 and the jack 8, and the windng of cut-oil relay 5 to ground. Relay 12, in operating, completes the hereinbeforeiio traced locking circuit for itself, and the supervisory lamp 13 is lighted over this circuit which includes the winding of relay l2, and the winding of cut-off relay 5. Cut-off relay 5*now operates, disconnecting the line relay 6 from the line. Relay 12, upon attracting-itsarmatures, also causes the operation of relay 9, which disconnects the polarized relay 1.0 from across the talking strands of thecord circuit, and closes the-normally open contacts in thetalking strands. Relay 1 2', in operating, also causes the operation of ringing relay 2'? over a circuit from battery through the winding of relay 27, normal contact of relay 25;, normal contact of key 20, normal contact of tripping relay 30, and the lower alternate contact of relay 12 to ground. Ringing relay 27, in operating, connects asource of ringing current 31 to line B, through the winding of tripping relay 30, for causing'the operation of theusual call bell 32 at station 13'. Subscriber B, in responding tot-he operation of this call bell 32, removes the receiver froln the switch hook, thereby causing the operation of trippi'ng relay 30, which removes the short circuit from about relay 25; Relay 25 is thereupon. included in circuit with the ringing relay 27, and is energized. Relay 25, upon being energized, closes its alternate and opens its normal. contact. The closure of the alternate contact of relay 25 establishes a locking circuit therefor and completes a direct short circuit for ringing relay 27, which releases, disconnecting ringing current from the called lin' Upon the release of ringing relay 27, supervisoryrelay 28 operates in the manner hereinbeforc described to extinguish supervisory lamp 13. At the conclusion of the conversation, the supervisory relays release to cause the supervisorylamps to be lighted to furnish disconnect signals, whereupon the operator may disconnect the cord circuit C from the two lines, restoring all apparatus to normal condition.

What is claimed is:

1. In a telephone exchange system, the combination of a telephone line, a link circuit comprising a pair of talking conductors, a relay bridged across the talking conductors, an energizing circuit for the relay completed by the connection of the link circuit with the telephone line, a source of ringing current, and a relay operating upon the energization of the bridged relay forconnecting the source of ringing current to the line.

2; In a telephone exchange system, the combination of a telephone line, a link circuit comprising a pair of talking conductors, a relay bridged across the talking conductors and energized upon the connection of thelink circuit with the telephoneiine, a second relay operating'uponthe energization of thebridged relay for disconnecting the bridged relay from the talking conduc tors, a source of ringing current, and a ringingrelay operating upon the energization of" the bridged relay for connecting the source of ringing current to the line.

3. In a telephone exchange system, the combination of a telephone line, a link cir: cuit comprising a pair of' normally open talking conductors, a relay bridged across the talking conductors and energized upon the connection ofthelink circuit with the tele phone line, a second relaopera-ting upon 'energization of thebridged relay, a locking circuit therefor established upon the operationthereof, a switching device rendered effective upon-theoperation of the second relay to disconnect the bridged relay from and to close the talking conductors, a source of ringing current, and a ringing relay energized upon the operation of'the second relay for connecting thesource of ringingcurrent to the line.

4. In a telephone exchange system, the combination of a telephone line extending from a. subscribers station to a centraloflice, a switch at the station adapted to close the telephone line, a link circuit at the central oflice comprising a pair of normally open talking conductors, a relay bridged across the talking conductors and energized upon the connection of the link circuit with the telephone line when the telephone line is open and not energized when the telephone line is closcd, a signaling device, interrupter mechanism,,and a relay operating upon the connection of the link circuit with the telephone line for including the interrupter mechanism' in circuit with the signaling device to cause the intermittent operation t-hereof'when the bridged relay is not energized.

5. In: a telephone exchange system, the combination of a telephone line extending from a subscriber s station to a central ofiice, a switch at the station adapted to close the telephone line, a, link circuit at the central oflicecomprising apair of normally open talking conductors, a relay bridged across the talking'conductors and energized upon the connection of. the link circuit with the telephone line when the telephone line-isopen and not energized when the telephone line is closed, a signaling device, interrupter mechanism, a relay operating upon theconnection of the link circuit with the telephone line for including; the interrupter mechanism in circuit with the-signaling device to cause the intermittent operation thereof when the bridged relay is not energized, a switching device, and a relay operating upon the momentary actuation of the switching devicefor causing-the closure of the talking conductors.

' 6. In a telephone exchange system, thecombination of a telephone line extending from a subscribers station to a. central oflice, a switch atthe station adapted to close the telephone line, a link circuit at the central office comprising a -pair of normally open talking conductors, a relay bridged across the talking conductors, and energized upon the connection of the link circuit with the telephone line henthe telephone line is open and not energized whenthetelephone line is closed, a signaling device, interrupter mechanism, a relay operating upon the connection of the link circuit with the telephone line for including the interrupter mechanism in circuit with thesignaling deviceto cause the intermittent operation thereof when the bridgedrelay is not energized, a switching device, a local relay energized upon the momentary actuation of the switching device to stop the intermittent operation of the signaling device, and a disconnect relay operating upon the energization of the local relay to disconnect the bridged relay-from and to close the talking conductors. p

7. In a telephone exchange system, the combination of a telephone line extending from a subscribers station to a central of.- fice, a switch at the station adapted to close the telephoneiline, a link circuit at the central oflice comprising a pair of normally open talking conductors, a relay bridged across the talking conductors and energized upon the connection of the link circuit with the telephone line when the telephoneline is open and not energized when the telephone line is closed, a signaling device, interrupter mechanism, a relay operating upon connection of the link circuit with the telephone line for including the interrupter mechanism in circuit with the signaling device to cause the intermittent operation thereof when the bridged relay is not energized, a switching device, a local relay energized upon the momentary actuation of the switching device to deenergize the second mentioned relay thereby to stop the in termittent operation of the signaling device, a locking circuit for the local relay established upon the operation thereof, and a disconnect relay energized upon the operation of the local relay to disconnect the bridged relay from and to close the talking conductors.

8. In a telephone exchange system, the

' combination of a telephone line extending from a subscribers station to a central office; a switch at the station adapted to close the telephone line; a link circuit at the central oliice comprising a pair of normally open talking conductors; a relay bridged across the talking conductors and energized upon the connection of the link circuit with the telephone line; when the telephone line is open and not energized when the telephone line is closed, and means for closing the talking conductors upon. the connection of the link circuit with the telephone line when closed comprising a switching device, and a relay energized upon the actuation of the switching device for causing the closure of the talking strands.

9. In a telephone exchange system, the combination of a telephone line extending from a subscribers station to a central oflice; a switch at the station adapted to close the telephone line; a link CllClllt at the central oilice comprising a pair of normally open talking conductors; a relay bridged across the talking conductors and energized upon the connection of the link circuit with the telephone line when the telephone line is open and not energized when the telephone line is closed; means for closing the talking conductors upon connection of the link circuit with the telephone line when closed comprising a switching device, a relay energized upon the momentary actuation of the switching device, a locking circuit therefor established upon the energization thereof, and a disconnect relay operating upon the energization of the last mentioned relay to disconnect the bridged relay close the talking conductors.

10. In a telephone exchange system, the combination of a plurality of telephone lines each terminating in a plurality of switching terminals, a plurality of link circuits having cooperating switching terminals each comprising a pair of talking conductors, a source of ringing current, a ringing relay in each link circuit for connecting the source of ringing current to a line upon the connection of the associated link circuit with a terminal thereof, a relay bridged across the talking conductors of each link circuit controlling the operation of the associated ringing relay, and meansrendered effective upon the connection of one link circuit with a terminal of one of the linesfor preventing the operation of the bridged relay of another link circuit when connected with another terminal of the same line.

11. In a telephone exchange system, the

combination of telephone lineseach termisource of ringing current to the associated from and to I line and means rendered effective upon the ductors, an operating circuit for the relay operation of the polarized relay of a busy completed by the connection of the link cirlink circuit for preventing the operation of cuit with the telephone line and a source of the polarized relay of another link circuit ringing current controlled by, and connected 5 uponv the connection thereof With another with the telephone line upon the operation 15 terminal of the same line. of, the relay.

12. In a telephone exchange system, the In Witness whereof, I hereunto subscribe combination of a telephone line, a link cirmy name this 29th day'of June A. D., 1917. cuit comprising a pair of talking conduc- 10 tors, a relay bridged across the talking con- HARRY W. MAODOUGALL.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents- Washington, D. G. 

